Today's internal combustion engines are electronically controlled by processor-based engine control units (ECUs). An ECU can control many aspects of the engine's operation, such as fuel quantity, ignition timing, variable valve timing (VVT), turbocharger output, and other engine operating parameters.
An ECU determines these parameters primarily by monitoring the engine through various sensors. These sensors can include a MAP (manifold air pressure) sensor, throttle position sensor, air temperature sensor, oxygen sensor, coolant temperature sensor, mass air flow sensor, crankshaft angle sensor, camshaft angle sensor, knock sensor, and many others. The ECU monitors the output signals produced by these sensors, and adjusts the system inputs as necessary.
Considerable effort is devoted to designing ECU programming that will provide optimal engine operation. Modern engines have nonlinear dynamics, and various nonlinear control methods have been developed.
One such nonlinear control method is “sliding mode control”, which is a control method having high robustness with restraining influence from disturbance. As examples, applications of sliding mode control have been developed for engine throttle control and cam phase control. These control methods are described in U.S. Pat. Nos. 6,367,449 and in 6,718,922, respectively.